Diagonal fan

ABSTRACT

A diagonal fan is disclosed and includes a frame and an impeller. The frame includes an inlet, an outlet, an accommodation space and a guiding wall. The inlet and the outlet are communicated through the accommodation space. The guiding wall is extended along an axial direction to the accommodation space. The impeller is accommodated within the accommodation space and includes a conical section shell. When the impeller is rotated, an airflow flowing is generated. The outer diameter of the hub of the impeller is expended gradually in a direction from the inlet toward the outlet, so that the flowing direction of the airflow is expended gradually around the peripheral of the impeller. A gap having a spacing distance is substantially maintained to form a backflow channel. A backflow is transported through an intake section, a horizontal section and an exhaust section of the backflow channel, and converged with the airflow.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 63/153,868 filed on Jul. 29, 2021, and entitled “DIAGONAL FAN”. This application also claims priority to China Patent Application No. 202210128548.9, filed on Feb. 11, 2022. The entireties of the above-mentioned patent application are incorporated herein by reference for all purposes.

FIELD OF THE INVENTION

The present disclosure relates to a diagonal fan, and more particularly to a diagonal fan having an optimized chamber to reduce the backflow flowing into the chamber and eliminate the turbulence area in the chamber, thereby achieving the purpose of improving the fan characteristics and reducing the noise.

BACKGROUND OF THE INVENTION

With the increasing amount of calculation and transmission required by the communication systems, the efficiency and power consumption of electronic components in the system need to be improved to cope with huge data calculations continuously. In order to maintain the normal operation of the equipment, it is necessary to remove the internal heat of the system effectively. In a conventional communication equipment on the current market, the fan is mainly used to perform the forced convection on the system to achieve the purpose of heat dissipation. However, under increasingly severe system conditions, how to improve the efficiency of the fan effectively and maintain the same noise level has always been the goal of the industry's efforts.

Therefore, there is a need of providing a diagonal fan having an optimized chamber to reduce the backflow flowing into the chamber and eliminate the turbulence area in the chamber, thereby achieving the purpose of improving the fan characteristics and reducing the noise, so as to obviate the drawbacks encountered by the prior arts.

SUMMARY OF THE INVENTION

An object of the present disclosure is to provide a diagonal fan having an optimized chamber to reduce the backflow flowing into the chamber and eliminate the turbulence area in the chamber, thereby achieving the purpose of improving the fan characteristics and reducing the noise.

Another object of the present disclosure is to provide a diagonal fan. The outer diameter of the hub of the impeller is expended gradually in a direction from the inlet toward the outlet so that the flowing direction of the airflow is expended gradually around a periphery of the impeller, thereby forming the main feature of the diagonal fan. The guiding wall disposed on the frame is staggered and overlapped with the upper end of the conical section shell of the impeller, the inlet diameter is less than the outlet diameter, and the upper end of the conical section shell is extended upwardly from the tips of the blades, so that the diagonal fan is allowed to achieve the characteristic of slowing down the stall region as a centrifugal fan. The inner wall surface of the frame and the outer wall and the upper end of the conical section shell are designed to be parallel to each other, and a spacing distance is substantially maintained between the inner wall surface of the frame, and the outer wall and the upper end of the conical section shell to form a backflow channel, so that as a backflow is sucked into the backflow channel through an intake section, the flow velocity and the kinetic energy of the flow field are reduced gradually. Therefore, the wind resistance between the inner wall surface of the frame, and the outer wall and the upper end of the conical section shell is increased, the backflow sucked into the backflow channel is reduced, and the turbulent flow intensity of the backflow channel is eliminated simultaneously. Furthermore, the balance holes on the impeller are arranged and corresponding to the horizontal section of the backflow channel. On the other hand, when the impeller is rotated, the backflow flows in the exhaust section along a direction identical to that of the airflow flowing. In this way, when the backflow is converged into the airflow, the collision of flowing field is less likely to occur.

In accordance with an aspect of the present disclosure, a diagonal fan is provided and includes a frame and an impeller. The frame includes an inlet, an outlet, an accommodation space and a guiding wall. The inlet and the outlet are disposed at two opposite sides of the frame, and in fluid communication with each other through the accommodation space. The impeller is accommodated within the accommodation space of the frame. When the impeller is rotated, an airflow flowing from the inlet to the outlet is generated. The outer diameter of a hub of the impeller is expended gradually in a direction from the inlet toward the outlet so that the flowing direction of the airflow is expended gradually around a periphery of the impeller. The impeller includes a conical section shell, and a spacing distance is substantially maintained between the inner wall surface of the frame, and an outer wall and an upper end of the conical section shell to form a backflow channel. The backflow channel includes an intake section, a horizontal section and an exhaust section, the intake section is located adjacent to a lower end of the conical section shell and in fluid communication with the exhaust section through the horizontal section, and the upper end of the conical section shell is at least partially shielded by the guiding wall to form the exhaust section. When the airflow flows from the inlet to the outlet, a backflow is transported from the intake section, flows through the horizontal section, is exhausted out through the exhaust section, and is converged with the airflow.

BRIEF DESCRIPTION OF THE DRAWINGS

The above contents of the present disclosure will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which:

FIG. 1 is a perspective view illustrating a diagonal fan according to a first embodiment of the present disclosure from an upper perspective;

FIG. 2 is a perspective view illustrating the diagonal fan according to the first embodiment of the present disclosure from a lower perspective;

FIG. 3 is an exploded view illustrating the diagonal fan according to the first embodiment of the present disclosure;

FIG. 4A is a perspective view illustrating the impeller according to the first embodiment of the present disclosure;

FIG. 4B is a cross-section view illustrating the impeller according to the first embodiment of the present disclosure;

FIG. 5 is a cross-section structural view illustrating the diagonal fan according to the first embodiment of the present disclosure;

FIG. 6 is a cross-section view illustrating the diagonal fan according to the first embodiment of the present disclosure;

FIG. 7 is an enlarged view showing the region P1 in FIG. 6 ;

FIG. 8A is a perspective view illustrating an impeller according to a second embodiment of the present disclosure;

FIG. 8B is a cross-section view illustrating the impeller according to the second embodiment of the present disclosure;

FIG. 9 is a cross-section view illustrating the diagonal fan according to the second embodiment of the present disclosure;

FIG. 10 is an enlarged view showing the region P2 in FIG. 9 ;

FIG. 11 is a perspective view illustrating a diagonal fan according to a third embodiment of the present disclosure;

FIG. 12 is a cross-section view illustrating the diagonal fan according to the third embodiment of the present disclosure;

FIG. 13 is an enlarged view showing the region P3 in FIG. 12 ;

FIG. 14 is a perspective view illustrating a diagonal fan according to a fourth embodiment of the present disclosure;

FIG. 15 is a cross-section view illustrating the diagonal fan according to the fourth embodiment of the present disclosure; and

FIG. 16 is an enlarged view showing the region P4 in FIG. 15 .

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present disclosure will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this disclosure are presented herein for purpose of illustration and description only. It is not intended to be exhaustive or to be limited to the precise form disclosed. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Further, spatially relative terms, such as “downwardly”, “upwardly”, “lower”, “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly. When an element is referred to as being “connected,” or “coupled,” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. Although the wide numerical ranges and parameters of the present disclosure are approximations, numerical values are set forth in the specific examples as precisely as possible. In addition, although the “first,” “second,” “third,” and the like terms in the claims be used to describe the various elements can be appreciated, these elements should not be limited by these terms, and these elements are described in the respective embodiments are used to express the different reference numerals, these terms are only used to distinguish one element from another element. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of example embodiments.

FIG. 1 is a perspective view illustrating a diagonal fan according to a first embodiment of the present disclosure from an upper perspective. In the embodiment, the diagonal fan 1 includes a frame 10 and impeller 40. The frame 10 includes an upper frame 20 and a lower frame 30 assembled with each other to form an accommodation space 100 for accommodating the impeller 40. In the embodiment, the upper frame 20 includes an inlet 50 and a guiding wall 22 disposed thereon. The guiding wall 22 is extended downwardly from a periphery of the inlet 50 along an axial direction C into the accommodation space 100. The impeller 40 include a hub 41 exposed through the inlet 50 under the axial direction C. In the embodiment, the upper frame 20 includes an upper frame plate 21, for example in a square shape, disposed on an upper end of the upper frame 20. The inlet 50 is located on the upper frame 20. Preferably but not exclusively, the inlet 50 is circular and runs through the upper frame plate 21. Preferably but not exclusively, the guiding wall 22 is an annular curved surface in appearance and connected to the upper frame plate 21. The guiding wall 22 is extended downwardly from the periphery of the inlet 50 into the accommodation space 100 so that the air is introduced into the accommodation space 100 when the impeller 40 is rotated.

FIG. 2 is a perspective view illustrating the diagonal fan according to the first embodiment of the present disclosure from a lower perspective. In the embodiment, the lower frame 30 includes a lower frame plate 31, a base 32 and a plurality of static blades 33. The lower frame plate 31 is spatially corresponding to the upper frame plate 21. Preferably but not exclusively, the upper frame plate 21 and the lower frame plate 31 are approximately parallel to each other. The plurality of static blades 33 are disposed between the base 32 and the lower frame plate 31, and two ends of each of the static blades 33 are connected to the base 32 and the lower frame plate 31, respectively, so as to form an outlet 60. In that, the outlet 60 is located between the lower frame plate 31 and the base 32. When the impeller 40 is rotated, the air in the accommodation space 100 is allowed to flow through the plurality of static blades 33, between the base 32 and the lower frame plate 31, and be discharged out through the outlet 60.

FIG. 3 is an exploded view illustrating the diagonal fan according to the first embodiment of the present disclosure. In the embodiment, the frame 10 is formed by assembling the upper frame 20 and the lower frame 30. Preferably but not exclusively, the upper frame 20, the impeller 40 and the lower frame 30 are arranged along the axial direction C so that the impeller 40 is allowed to be placed in the accommodation space 100 when the upper frame 20 and the lower frame 30 are assembled together. In the embodiment, the impeller 40 includes a hub 41, a cylindrical part 42, a conical section shell 43, a plurality of blades 44 and a plurality of balance holes 45. The plurality of blades 44 of the impeller 40 are connected between the hub 41 and the conical section shell 43. The plurality of balance holes 45 are disposed on a flat annular plane of the upper end of the conical section shell 43. In other embodiments, the number, the shape and the size of the balance holes 45 are adjustable according to the practical requirements. The present disclosure is not limited thereto.

FIG. 4A is a perspective view illustrating the impeller according to the first embodiment of the present disclosure. In the embodiment, the hub 41, the cylindrical part 42, the conical section shell 43, the plurality of blades 44 and the plurality of balance holes 45 are integrally formed as a one piece by injection molding. The cylindrical part 42 is extended axially from a lower end of the hub 41. The conical section shell 43 and the hub 41 are arranged concentrically with each other, and the conical section shell 43 is connected to the periphery of the hub 41 through the plurality of blades 44. In the embodiment, each of the plurality of blades 44 is three-dimensionally curved. Preferably but not exclusively, each of the blades 44 includes an inner end connected to the hub 41 and an outer end connected to the inner annular wall of the conical section shell 43. As the cylindrical part 42 drives the hub 41, the plurality of blades 44 and the conical section shell 43 to rotate, the air is driven to flow among the hub 41, the plurality of blades 44 and the conical section shell 43.

FIG. 4B is a cross-section view illustrating the impeller according to the first embodiment of the present disclosure. In the embodiment, the plurality of blades 44 are disposed around the periphery of the hub 41, and the upper end of the conical section shell 43 is extended upwardly from the upper tips of the blades 44 so that the upper end of the conical section shell 43 is higher than the upper end of the hub 41 and the tips of the plurality of blades 44 connected with the conical section shell 43. The upper end of the hub 41 is lower than the upper end of the conical section shell 43. The outer diameter of the hub 41 of the impeller 40 is expended gradually in a direction from the inlet 50 toward the outlet 60.

FIG. 5 is a cross-section structural view illustrating the diagonal fan according to the first embodiment of the present disclosure. In the embodiment, the base 32 of the lower frame 30 further includes a tube 34. Preferably but not exclusively, the stator includes a winding 80 and a printed circuit board 81. The winding 80 and the printed circuit board 81 are disposed on a periphery of the tube 34. The rotator includes a magnetic shell 70, a magnet 71 and a shaft 72. The magnetic shell 70 is disposed within the cylindrical part 42 of the impeller 40 and connected to the shaft 72. In the embodiment, the magnet 71 is disposed on a radially inner wall of the magnetic shell 70 and spatially corresponding to the winding 80. The shaft 72 is disposed at the center of the magnetic shell 70, and is disposed in the tube 34 through at least one bearing 73. On the other hand, in the embodiment, the guiding wall 22 is extended downwardly from the periphery of the inlet 50, and the upper end of the conical section shell 43 is extended upwardly from the outer ends of the blades 44, so that the upper frame 20 of the frame 10, the upper end of the conical section shell 43 and the guiding wall 22 are at least partially overlapped in view of the radial direction. The integrally formed upper frame body 20 and the guiding wall 22 are substantially parallel to the outer wall of the conical section shell 43 adjacent to the inlet 50 so that a backflow channel 90 is formed among the upper frame 20 of the frame 10, the outer side of the conical section shell 43 and the inner side of the guiding wall 22. Preferably but not exclusively, the backflow channel 90 is curved in multiple sections, so as to change the flow direction thereof.

FIG. 6 is a cross-section view illustrating the diagonal fan according to the first embodiment of the present disclosure. In the embodiment, the rotor and the stator are accommodated between the impeller 40 and lower frame 30. A chamber 36 is formed between a base wall 35 of the base 32 and tube 34, and configured to accommodate an electronic component 82 on the printed circuit board 81. The upper end of the base 32 is spatially corresponding to a periphery of the cylindrical part 42. In the embodiment, the impeller 40 is rotated to form the airflow AF from the inlet 50 to the outlet 60. The inlet 50 and the outlet 60 are arranged substantially along the axial direction C. The airflow AF is inhaled through the inlet 50, flowing among the plurality of blades 44, the hub 41 and the conical section shell 43, transported among the static blades 33, the base 32 and the lower frame plate 31, and discharged out through the outlet 60. Since the outer diameter of the hub 41 of the impeller 40 is expended gradually in the direction from the inlet 50 toward the outlet 60, the airflow AF is expanded gradually around the periphery of the impeller 40. In the embodiment, the frame 10 has a frame diameter OD1, the inlet 50 has an inlet diameter ID1, and the outlet 60 has an outlet diameter ID2. Preferably but not exclusively, the inlet diameter ID1 is less than the outlet diameter ID2. In the embodiment, a ratio of the inlet diameter ID1 to the frame diameter OD1 is ranged from 0.5 to 0.7. Preferably but not exclusively, the ratio of the inlet diameter ID1 to the frame diameter OD1 is 0.56. In the embodiment, a ratio of the outlet diameter ID2 to the frame diameter OD1 is ranged from 0.8 to 0.98. Preferably but not exclusively, the ratio of the outlet diameter ID2 to the frame diameter OD1 is 0.97. The inlet diameter ID1 is less than the outlet diameter ID2, and the upper end of the conical section shell 43 is extended upwardly from the tips of the blades 44.

FIG. 7 is an enlarged view showing the region P1 shown in FIG. 6 . In the embodiment, a gap having a spacing distance G is substantially maintained between an inner wall surface 110 of the upper frame 20 and an outer wall 430 of the upper end of the conical section shell 43 to form the aforementioned backflow channel 90. In the embodiment, a ratio of the spacing distance G to the frame diameter OD1 (referring to FIG. 6 ) is ranged from 0.01 to 0.02. Preferably but not exclusively, the ratio of the spacing distance G to the frame diameter OD1 is ranged from 0.0125. In the embodiment, the backflow channel 90 includes an intake section 91, a horizontal section 92 and an exhaust section 93. The intake section 91 is located adjacent to a lower end of the conical section shell 43 and in fluid communication with the exhaust section 93 through the horizontal section 92, and the upper end of the conical section shell 43 is at least partially shielded by the guiding wall 22 to form the exhaust section 93. Notably, the backflow BF flows in the intake section 91 along a direction reversed to that of the backflow BF flowing in the exhaust section 93. The backflow BF flows in the horizontal section 92 along a direction perpendicular to the axial direction C. The backflow BF flows in the exhaust section 93 along a direction identical to that of the airflow AF flowing. Since the inner wall surface 110 of the frame 10 and the outer wall 430 and the upper end of the conical section shell 43 are designed to be parallel to each other, and the gap having the spacing distance G is substantially maintained between the inner wall surface 110 of the frame 10, and the outer wall 430 and the upper end of the conical section shell 43 to form the backflow channel 90 curved in multiple sections, as the backflow BF is sucked into the backflow channel 90 through the intake section 91, the flow velocity and the kinetic energy of the flow field are reduced gradually. Therefore, the wind resistance between the inner wall surface 110 of the frame 10, and the outer wall 430 and the upper end of the conical section shell 43 is increased, the backflow BF sucked into the backflow channel 90 is reduced, and the turbulent flow intensity of the backflow channel 90 is eliminated simultaneously. In the embodiment, the conical section shell 43 includes the plurality of balance holes 45 disposed around the upper end of the conical section shell 43, and the horizontal section 92 is spatially corresponding to the plurality of balance holes 45. In the embodiment, the corresponding lengths of the intake section 91, the horizontal section 92 and the exhaust section 93 are varied and bent by adjusting the frame 10, the impeller 40 and the guiding wall 22. In other embodiments, the corresponding lengths and the relative bending angles of the intake section 91, the horizontal section 92 and the exhaust section 93 are adjustable according to the practical requirements. The present disclosure is not limited thereto.

FIG. 8A is a perspective view illustrating an impeller according to a second embodiment of the present disclosure. In the embodiment, the impeller 40 a includes a hub 41, a cylindrical part 42, a conical section shell 43, a plurality of blades 44 and a plurality of balance holes 45. The lower end of the hub 41 is connected to the cylindrical part 42, and the hub 41 and the cylindrical part 42 are integrally formed as a single piece by injection molding. Preferably but not exclusively, the conical section shell 43 and the hub 41 are arranged concentrically with each other, and the conical section shell 43 is connected to the outer part of the hub 41 through the plurality of blades 44. In the embodiment, each of the plurality of blades 44 is three-dimensionally curved. Preferably but not exclusively, each of the blades 44 includes an inner end connected to the hub 41 and an outer end connected to the inner ring wall of the conical section shell 43. As the cylindrical part 42 drives the hub 41, the plurality of blades 44 and the conical section shell 43 to rotate, the air is driven to flow among the hub 41, the plurality of blades 44 and the conical section shell 43. The lower end of the conical section shell 43 is protruded outwardly in the radial direction so as to form an annular plane. Preferably but not exclusively, the plurality of balance holes 45 are annularly arranged at the lower end of the conical section shell 43 and located at the annular plane protruded outwardly from the lower end of the conical section shell 43. Moreover, the opening of each of balance holes 45 is faced upwardly.

FIG. 8B is a cross-section view illustrating the impeller according to the second embodiment of the present disclosure. In the embodiment, the plurality of blades 44 are disposed around the periphery of the hub 41, and the upper end of the conical section shell 43 is extended upwardly from the tips of the blades 44. In addition, a flat annular plane is formed on the upper end of the conical section shell 43. Preferably but not exclusively, the flat annular plane is higher than the tips of the plurality of blades 44 connected to the conical section shell 43, and is also higher than the upper end of the hub 41. Preferably but not exclusively, in the embodiment, the cylindrical par 42 is annular and includes a hollow portion, which is configured to accommodate the rotor and the stator, so that the impeller 40 a is driven by the rotor and the stator to rotate. In conjunction with the change in the design of the balance holes 45, it helps to increase the varied applications of the impeller 40 a.

FIG. 9 is a cross-section view illustrating the diagonal fan according to the second embodiment of the present disclosure. In the embodiment, when the impeller 40 a is rotated, an airflow AF is formed to flow from the inlet 50 to the outlet 60. The inlet 50 and the outlet 60 are substantially arranged along the axial direction C. The airflow AF is inhaled through the inlet 50, flowing among the plurality of blades 44, the hub 41 and the conical section shell 43, transported among the static blade 33, the base 32 and the lower frame plate 31, and discharged out through the outlet 60. Since the outer diameter of the hub 41 of the impeller 40 a is expended gradually in the direction from the inlet 50 toward the outlet 60, the airflow AF is expanded gradually around the periphery of the impeller 40 a. In the embodiment, the frame 10 has a frame diameter OD1, the inlet 50 has an inlet diameter ID1, and the outlet 60 has an outlet diameter ID2. Preferably but not exclusively, the inlet diameter ID1 is less than the outlet diameter ID2. In the embodiment, a ratio of the inlet diameter ID1 to the frame diameter OD1 is ranged from 0.5 to 0.7. Preferably but not exclusively, the ratio of the inlet diameter IDI to the frame diameter OD1 is 0.56. In the embodiment, a ratio of the outlet diameter ID2 to the frame diameter OD1 is ranged from 0.8 to 0.98. Preferably but not exclusively, the ratio of the outlet diameter ID2 to the frame diameter OD1 is 0.97.

FIG. 10 is an enlarged view showing the region P2 in FIG. 9 . In the embodiment, a gap having a spacing distance G is substantially maintained between an inner wall surface 110 of the upper frame 20 and an outer wall 430 of the upper end of the conical section shell 43 to form the aforementioned backflow channel 90. In the embodiment, a ratio of the spacing distance G to the frame diameter OD1 (referring to FIG. 9 ) is ranged from 0.01 to 0.02. Preferably but not exclusively, the ratio of the spacing distance G to the frame diameter OD1 is ranged from 0.0125. In the embodiment, the backflow channel 90 includes an intake section 91, a first horizontal section 921, a second horizontal section 922, a communication section 923 and an exhaust section 93. The intake section 91 is located adjacent to the lower end of the conical section shell 43, and in fluid communication with the exhaust section 93 through the first horizontal section 921, the communication section 923 and the second horizontal section 922, sequentially. Moreover, the upper end of the conical section shell 43 is at least partially shielded by the guiding wall 22 to form the exhaust section 93. Notably, the backflow BF flows in the intake section 91 along a direction, which is reversed to the direction of the backflow BF flowing in the exhaust section 93 and parallel to the axial direction C. The backflow BF flows in the first horizontal section 921 along a direction, which is perpendicular to the axial direction C and perpendicular to the intake section 91. The backflow BF flows in the second horizontal section 922 along a direction, which is perpendicular to the axial direction C and perpendicular to the exhaust section 93. The backflow BF flows in the exhaust section 93 along a direction identical to that of the airflow AF flowing. In the embodiment, the conical section shell 43 includes a plurality of balance holes 45 disposed around the lower end of the conical section shell 43. The first horizontal section 921 is spatially corresponding to the plurality of balance holes 45, and the backflow BF flows in the first horizontal section 921 along the direction perpendicular to the axial direction C. In the embodiment, the inner wall surface 110 of the frame 10 and the outer wall 430 and the upper end of the conical section shell 43 are designed to be parallel to each other, and a gap having a spacing distance G is substantially maintained between the inner wall surface 110 of the frame 10, and the outer wall 430 and the upper end of the conical section shell 43 to form the backflow channel 90 curved in multiple sections. Preferably but not exclusively, the backflow channel 90 includes at least two vertical bending portions. As the backflow BF is sucked into the backflow channel 90 through the intake section 91, the flow velocity and the kinetic energy of the flow field are reduced gradually. Therefore, the wind resistance between the inner wall surface 110 of the frame 10, and the outer wall 430 and the upper end of the conical section shell 43 is increased, the backflow BF sucked into the backflow channel 90 is reduced, and the turbulent flow intensity of the backflow channel 90 is eliminated simultaneously.

FIG. 11 is a perspective view illustrating a diagonal fan according to a third embodiment of the present disclosure. In the embodiment, the structures, elements and functions of the diagonal fan 1 b are similar to those of the diagonal fan 1 of FIGS. 1 to 3 , and are not redundantly described herein. In the embodiment, the diagonal fan 1 b is of a flat design, and the frame 10 is formed by assembling an upper frame 20 and a lower frame 30. The accommodation space 100 is configured to accommodate the impeller 40 b. In the embodiment, the inlet 50 and the guiding wall 22 are disposed on the upper frame 20. Preferably but not exclusively, the upper frame 20 includes a square upper frame plate 21 disposed at the upper end of the upper frame 20. The inlet 50 is located on the upper frame 20. Preferably but not exclusively, the inlet 50 is circular and runs through the upper frame plate 21. The guiding wall 22 is connected to the upper frame plate 21 and extended downwardly from the periphery of the inlet 50 into the accommodation space 100, so that the air is introduced into the accommodation space 100 when the impeller 40 b is rotated. In addition, the upper end of the hub 41 includes a flat plane.

FIG. 12 is a cross-section view illustrating the diagonal fan according to the third embodiment of the present disclosure. In the embodiment, when the impeller 40 b is rotated, an airflow AF is formed to flow from the inlet 50 to the outlet 60. The inlet 50 and the outlet 60 are arranged along the axial direction C. The airflow AF is inhaled through the inlet 50, flowing among the plurality of blades 44, the hub 41 and the conical section shell 43, transported among the static blade 33, the base 32 and the lower frame plate 31, and discharged out through the outlet 60. Since the outer diameter of the hub 41 of the impeller 40 b is expended gradually in the direction from the inlet 50 toward the outlet 60, the airflow AF is expanded gradually around the periphery of the impeller 40 b. In the embodiment, the frame 10 has a frame diameter OD1, the inlet 50 has an inlet diameter ID1, and the outlet 60 has an outlet diameter ID2. Preferably but not exclusively, the inlet diameter ID1 is less than the outlet diameter ID2. In the embodiment, a ratio of the inlet diameter ID1 to the frame diameter OD1 is ranged from 0.6 to 0.8. Preferably but not exclusively, the ratio of the inlet diameter ID1 to the frame diameter OD1 is 0.74. In the embodiment, a ratio of the outlet diameter ID2 to the frame diameter OD1 is ranged from 0.8 to 0.98. Preferably but not exclusively, the ratio of the outlet diameter ID2 to the frame diameter OD1 is 0.975.

FIG. 13 is an enlarged view showing the region P3 in FIG. 12 . In the embodiment, a gap having a spacing distance G is substantially maintained between an inner wall surface 110 of the upper frame 20 and an outer wall 430 and the upper end of the conical section shell 43 to form the aforementioned backflow channel 90. In the embodiment, a ratio of the spacing distance G to the frame diameter OD1 (referring to FIG. 12 ) is ranged from 0.01 to 0.02. Preferably but not exclusively, the ratio of the spacing distance G to the frame diameter OD1 is ranged from 0.0125. In the embodiment, the backflow channel 90 includes an intake section 91, a horizontal section 92 and an exhaust section 93. The intake section 91 is located adjacent to a lower end of the conical section shell 43 and in fluid communication with the exhaust section 93 through the horizontal section 92, and the upper end of the conical section shell 43 is at least partially shielded by the guiding wall 22 to form the exhaust section 93. Notably, the backflow BF flows in the intake section 91 along a direction reversed to that of the backflow BF flowing in the exhaust section 93. The backflow BF flows in the horizontal section 92 along a direction perpendicular to the axial direction C. The backflow BF flows in the exhaust section 93 along a direction identical to that of the airflow AF flowing. Since the inner wall surface 110 of the frame 10 and the outer wall 430 and the upper end of the conical section shell 43 are designed to be parallel to each other, and the gap having the spacing distance G is substantially maintained between the inner wall surface 110 of the frame 10, and the outer wall 430 and the upper end of the conical section shell 43 to form the backflow channel 90, as the backflow BF is sucked into the backflow channel 90 through the intake section 91, the flow velocity and the kinetic energy of the flow field are reduced gradually. Therefore, the wind resistance between the inner wall surface 110 of the frame 10, and the outer wall 430 and the upper end of the conical section shell 43 is increased, the backflow BF sucked into the backflow channel 90 is reduced, and the turbulent flow intensity of the backflow channel 90 is eliminated simultaneously. Preferably but not exclusively, in the embodiment, the arrangement of the aforementioned balance holes 45 is omitted in the impeller 40 b, and the horizontal section 92 is spatially corresponding to the annular plane of the upper end of the conical section shell 43. On the other hand, when the impeller 40 b is rotated, the backflow BF flows in the exhaust section 93 of the backflow channel 90 along a direction identical to that of the airflow AF flowing. In this way, when the backflow BF is converged into the airflow AF, the collision of flowing field is less likely to occur and the noise during operation is reduced.

FIG. 14 is a perspective view illustrating a diagonal fan according to a fourth embodiment of the present disclosure. In the embodiment, the structures, elements and functions of the diagonal fan 1 c are similar to those of the diagonal fan 1 b of FIGS. 11 to 12 , and are not redundantly described herein. In the embodiment, the diagonal fan 1 c is of a flat design, and the frame 10 is formed by assembling an upper frame 20 and a lower frame 30. Preferably but not exclusively, the upper frame 20 is a plate-like structure, and covered on the lateral walls of the lower frame 30 to form an accommodation space 100 configured to accommodate the impeller 40 c. In the embodiment, the inlet 50 and the guiding wall 22 are disposed on the upper frame 20. Preferably but not exclusively, the upper frame 20 is a square upper frame plate 21 disposed on the upper end of the lower frame 30. The guiding wall 22 is connected to the upper frame plate 21 and extended downwardly from the periphery of the inlet 50 into the accommodation space 100, so that the air is introduced into the accommodation space 100 when the impeller 40 c is rotated. Preferably but not exclusively, the upper end of the hub 41 includes a flat plane.

FIG. 15 is a cross-section view illustrating the diagonal fan according to the fourth embodiment of the present disclosure. In the embodiment, when the impeller 40 c is rotated, an airflow AF is formed to flow from the inlet 50 to the outlet 60. The inlet 50 and the outlet 60 are arranged along the axial direction C. The airflow AF is inhaled through the inlet 50, flowing among the plurality of blades 44, the hub 41 and the conical section shell 43, transported among the static blade 33, the base 32 and the lower frame plate 31, and discharged out through the outlet 60. Since the outer diameter of the hub 41 of the impeller 40 c is expended gradually in the direction from the inlet 50 toward the outlet 60, the airflow AF is expanded gradually around the periphery of the impeller 40 c. In the embodiment, the frame 10 has a frame diameter OD1, the inlet 50 has an inlet diameter ID1, and the outlet 60 has an outlet diameter ID2. Preferably but not exclusively, the inlet diameter ID1 is less than the outlet diameter ID2. In the embodiment, a ratio of the inlet diameter ID1 to the frame diameter OD1 is ranged from 0.6 to 0.8. Preferably but not exclusively, the ratio of the inlet diameter ID1 to the frame diameter OD1 is 0.74. In the embodiment, a ratio of the outlet diameter ID2 to the frame diameter OD1 is ranged from 0.8 to 0.98. Preferably but not exclusively, the ratio of the outlet diameter ID2 to the frame diameter OD1 is 0.975.

FIG. 16 is an enlarged view showing the region P4 in FIG. 15 . In the embodiment, a gap having a spacing distance G is substantially maintained between an inner wall surface 110 of the lower frame 30 and an outer wall 430 and the upper end of the conical section shell 43 to form the aforementioned backflow channel 90. In the embodiment, a ratio of the spacing distance G to the frame diameter OD1 (referring to FIG. 15 ) is ranged from 0.01 to 0.02. Preferably but not exclusively, the ratio of the spacing distance G to the frame diameter OD1 is ranged from 0.0125. In the embodiment, the backflow channel 90 includes an intake section 91, a horizontal section 92 and an exhaust section 93. The intake section 91 is located adjacent to a lower end of the conical section shell 43 and in fluid communication with the exhaust section 93 through the horizontal section 92, and the upper end of the conical section shell 43 is at least partially shielded by the guiding wall 22 to form the exhaust section 93. Preferably but not exclusively, in the embodiment, the inner wall surface 110 of the lower frame 30 and the outer wall 430 of the conical section shell 43 are parallel to the axial direction C. Notably, the backflow BF flows in the intake section 91 along a direction reversed to that of the backflow BF flowing in the exhaust section 93. The backflow BF flows in the horizontal section 92 along a direction, which is perpendicular to the axial direction C and also perpendicular to the intake section 91 and the exhaust section 93. The backflow BF flows in the exhaust section 93 along a direction identical to that of the airflow AF flowing. In the embodiment, the conical section shell 43 includes a plurality of balance holes 45 disposed around the upper end of the conical section shell 43. The horizontal section 92 is spatially corresponding to the plurality of balance holes 45, and the backflow BF flows in the horizontal section 92 along the direction perpendicular to the axial direction C. Since the inner wall surface 110 of the frame 10 and the outer wall 430 and the upper end of the conical section shell 43 are designed to be parallel to each other, and the gap having the spacing distance G is substantially maintained between the inner wall surface 110 of the frame 10, and the outer wall 430 and the upper end of the conical section shell 43 to form the backflow channel 90 including at least two vertical bending portions, as the backflow BF is sucked into the backflow channel 90 through the intake section 91, the flow velocity and the kinetic energy of the flow field are reduced gradually. Therefore, the wind resistance between the inner wall surface 110 of the frame 10, and the outer wall 430 and the upper end of the conical section shell 43 is increased, the backflow BF sucked into the backflow channel 90 is reduced, and the turbulent flow intensity of the backflow channel 90 is eliminated simultaneously. In the embodiment, the conical section shell 43 includes the plurality of balance holes 45 disposed around the upper end of the conical section shell 43, and the horizontal section 92 is spatially corresponding to the plurality of balance holes 45. Moreover, the horizontal section 92 is perpendicular to the intake section 91 and the exhaust section 93, and in communication between the intake section 91 and the exhaust section 93. In other words, the balance holes 45 on the impeller 40 c are arranged and corresponding to the horizontal section 92 of the backflow channel 90. On the other hand, when the impeller 40 c is rotated, the backflow BF flows in the exhaust section 93 of the backflow channel 90 along a direction identical to that of the airflow AF flowing. In this way, when the backflow BF is converged into the airflow AF, the collision of flowing field is less likely to occur and the noise during operation is reduced. Certainly, the diagonal fan 1 c in the present disclosure is allowed to be combined and adjusted with the aforementioned technical features according to the practical requirements. In addition, the detailed structure of the backflow channel 90 in the present disclosure is adjustable according to the practical requirements. The present disclosure is not limited thereto.

In summary, the present disclosure provides a diagonal fan having an optimized chamber to reduce the backflow flowing into the chamber and eliminate the turbulence area in the chamber, thereby achieving the purpose of improving the fan characteristics and reducing the noise. The guiding wall disposed on the frame is staggered and overlapped with the upper end of the conical section shell of the impeller, the inlet diameter is less than the outlet diameter, and the upper end of the conical section shell is extended upwardly from the tips of the blades, so that the diagonal fan is allowed to achieve the characteristic of slowing down the stall region as a centrifugal fan. The inner wall surface of the frame and the outer wall and the upper end of the conical section shell are designed to be parallel to each other, and a gap having a spacing distance is substantially maintained between the inner wall surface of the frame, and the outer wall and the upper end of the conical section shell to form a backflow channel, so that as a backflow is sucked into the backflow channel through an intake section, the flow velocity and the kinetic energy of the flow field are reduced gradually. Therefore, the wind resistance between the inner wall surface of the frame, and the outer wall and the upper end of the conical section shell is increased, the backflow sucked into the backflow channel is reduced, and the turbulent flow intensity of the backflow channel is eliminated simultaneously. On the other hand, when the impeller is rotated, the backflow flows in the exhaust section along a direction identical to that of the airflow flowing. In this way, when the backflow is converged into the airflow, the collision of flowing field is less likely to occur and the noise during operation is reduced.

While the disclosure has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the disclosure needs not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures. 

What is claimed is:
 1. A diagonal fan, comprising: a frame comprising an inlet, an outlet, an accommodation space and a guiding wall, wherein the inlet and the outlet are disposed at two opposite sides of the frame, respectively, and in fluid communication with each other through the accommodation space, wherein the guiding wall is connected to an inner wall surface of the frame, and the guiding wall is extended from a periphery of the inlet along an axial direction into the accommodation space; and an impeller accommodated within the accommodation space of the frame, wherein when the impeller is rotated, an airflow flowing from the inlet to the outlet is generated, wherein the impeller comprises a conical section shell, and a gap having a spacing distance is substantially maintained between the inner wall surface of the frame, and an outer wall and an upper end of the conical section shell to form a backflow channel, wherein the impeller comprises a hub, and the outer diameter of the hub of the impeller is expended gradually in a direction from the inlet toward the outlet so that the flowing direction of the airflow is expended gradually around a periphery of the impeller.
 2. The diagonal fan according to claim 1, wherein the backflow channel comprises an intake section, a horizontal section and an exhaust section, the intake section is located adjacent to a lower end of the conical section shell and in fluid communication with the exhaust section through the horizontal section, and the upper end of the conical section shell is at least partially shielded by the guiding wall to form the exhaust section, wherein when the airflow flows from the inlet to the outlet, a backflow is transported from the intake section, flows through the horizontal section, is exhausted out through the exhaust section, and is converged with the airflow.
 3. The diagonal fan according to claim 2, wherein the conical section shell comprises a plurality of balance holes disposed around the upper end of the conical section shell, and the horizontal section is spatially corresponding to the plurality of balance holes.
 4. The diagonal fan according to claim 2, wherein the conical section shell comprises a plurality of balance holes disposed around the lower end of the conical section shell, the horizontal section is spatially corresponding to the plurality of balance holes, and the backflow channel further comprises a second horizontal section spatially corresponding to the upper end of the conical section shell.
 5. The diagonal fan according to claim 2, wherein the backflow flows in the intake section along a direction reversed to that of the backflow flowing in the exhaust section.
 6. The diagonal fan according to claim 2, wherein the backflow flows in the horizontal section along a direction perpendicular to the axial direction.
 7. The diagonal fan according to claim 2, wherein the backflow flows in the exhaust section along a direction identical to that of the airflow flowing.
 8. The diagonal fan according to claim 1, wherein the impeller comprises the hub, a cylindrical part and a plurality of blades, wherein the cylindrical part is configured to accommodate a rotor and a stator, the hub is disposed on the cylindrical part, the plurality of blade are spaced apart and disposed on the hub, and the plurality of blades are connected between the hub and the conical section shell, wherein when the impeller is rotated, the airflow is formed to flow through the plurality of blades and between the hub and the conical section shell.
 9. The diagonal fan according to claim 8, wherein the frame comprises an upper frame and a lower frame assembled with each other to form the inlet, the outlet and the accommodation space, wherein the inlet and the guiding wall are disposed on the upper frame.
 10. The diagonal fan according to claim 9, wherein the upper frame comprises an upper frame plate disposed on an upper end of the upper frame, the inlet is located at the upper frame, and the guiding wall is connected to the upper frame plate and extended downwardly from the periphery of the inlet into the accommodation space.
 11. The diagonal fan according to claim 10, wherein the lower frame comprises a lower frame plate, a base and a plurality of static blades, the lower frame plate is spatially corresponding to the upper frame plate, and the plurality of static blades are disposed between the base and the lower frame plate to form the outlet between the lower frame plate and base.
 12. The diagonal fan according to claim 11, wherein the base further comprises a tube, the stator comprises a winding and a printed circuit board disposed on a periphery of the tube, and the rotor comprises a magnetic shell, a magnet and a shaft, wherein the magnetic shell is disposed within the cylindrical part of the impeller and configured to accommodate the magnet, the shaft, the winding and a part of the tube, the magnet is disposed on an inner wall of the magnetic shell and spatially corresponding to the winding, the shaft is disposed at a center of the magnetic shell, and the shaft is disposed in the tube through a bearing.
 13. The diagonal fan according to claim 12, wherein a chamber is formed between the base and the tube, and configured to accommodate an electronic component on the printed circuit board.
 14. The diagonal fan according to claim 1, wherein the inlet has an inlet diameter, the outlet has an outlet diameter, and the inlet diameter is less than the outlet diameter.
 15. The diagonal fan according to claim 1, wherein the frame has a frame diameter, the inlet has an inlet diameter, the outlet has an outlet diameter, a ratio of the inlet diameter to the frame diameter is ranged from 0.5 to 0.7, and a ratio of the outlet diameter to the frame diameter is ranged from 0.8 to 0.98.
 16. The diagonal fan according to claim 1, wherein the frame has a frame diameter, the inlet has an inlet diameter, the outlet has an outlet diameter, a ratio of the inlet diameter to the frame diameter is ranged from 0.6 to 0.8, and a ratio of the outlet diameter to the frame diameter is ranged from 0.8 to 0.98.
 17. The diagonal fan according to claim 1, wherein the frame has a frame diameter, and a ratio of the spacing distance to the frame diameter is ranged from 0.01 to 0.02.
 18. The diagonal fan according to claim 1, wherein the frame, the upper end of the conical section shell and the guiding wall are at least partially overlapped in view of a radial direction. 